Forwardport #44668 from legacy to alpha: Set detailsURL in update XML to be useful for 13.5 users

⬅️ Backport Patchset

Bookkeeping

Issue(s)

• #44668 (closed)

Merge Request(s)

• !1880 (merged)

Target Channels

• Alpha
• Stable
• Legacy

Notes

We landed a patch in the 115esr 13.5 branch to use the unsupportedURL attribute of an <update> element. We're likely to want to reuse this logic in the future when deprecating other OSes. Therefore, we should land it in our development branch. Possibly also our stable 15.0 branch.

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